Dramatically enhanced degradation of recalcitrant organic contaminants in MgO2/Fe(III) Fenton-like system by organic chelating agents

Abstract

Herein, the application of organic acids as chelating agent, including citric acid (CA), tartaric acid (TA), oxalic acid (OA) and ethylenediaminetetraacetic acid (EDTA), to enhance the degradation performance of MgO₂/Fe(III) system was investigated in the terms of chelating agent dosage, Fe(III) dosage, reaction temperature, initial solution pH and inorganic anion. When the molar ratio of MgO₂/Fe(III)/chelating agent was 1 : 0.7 : 0.3, the degradation efficiencies of Rhodamine B (RhB) increased from 6.7% (without chelating agent) to 42.3%, 98.5%, 48.9% and 25.8% within 30 min for CA, TA, OA, and EDTA, respectively. The promotion effect was mainly attributed to the chelation between chelating agents and Fe(III), rather than the acidification of chelating agents. The pseudo-first-order kinetic model well fitted RhB degradation in MgO₂/Fe(III)/TA system, and the kinetic rate constant reached up to 0.295 min^-1. Hydroxyl radical was confirmed to be the dominant active species to degrade organics in the MgO₂/Fe(III)/TA system. Notably, the degradation system could work in a broad pH (3-11) and temperature (5-35 °C) range. Moreover, the MgO₂/Fe(III)/TA system can also effectively degrade methylene blue, tetracycline and bisphenol A. This work provided a new, efficient and environmentally-friendly Fenton-like system for stubborn contaminant treatment.

Keywords: Chelating agent; Fenton-like reaction; Hydroxyl radical; Magnesium peroxide nanoparticle; Organic contaminant.